class RuboCop::Cop::Performance::Sum


[1, 2, 3].sum(10, &:count)
[1, 2, 3].sum { |elem| elem ** 2 }
[1, 2, 3].sum(10)
# good
[1, 2, 3].collect(&:count).sum(10)
[1, 2, 3].map { |elem| elem ** 2 }.sum
[1, 2, 3].reduce(10, :+)
# bad
@example OnlySumOrWithInitialValue: true
[1, 2, 3].sum(10, &:count)
[1, 2, 3].sum { |elem| elem ** 2 }
[1, 2, 3].sum(10)
[1, 2, 3].sum
# good
[1, 2, 3].collect(&:count).sum(10)
[1, 2, 3].map { |elem| elem ** 2 }.sum
[1, 2, 3].reduce(10, :+)
[1, 2, 3].reduce { |acc, elem| acc + elem } # They can be prohibited completely using ‘SafeAutoCorrect: true`.
[1, 2, 3].inject(&:+) # and will only be performed when using the `-A` option.
[1, 2, 3].inject(:+) # Autocorrections for cases without initial value are unsafe
# bad
@example OnlySumOrWithInitialValue: false (default)
—-
[’H’, ‘e’, ‘l’, ‘l’, ‘o’].sum # => in ‘+’: String can’t be coerced into Integer (TypeError)
[1, 2, 3].sum # => 6
[].sum # => 0
[‘H’, ‘e’, ‘l’, ‘l’, ‘o’].reduce(:+) # => “Hello”
[1, 2, 3].reduce(:+) # => 6
[].reduce(:+) # => nil
—-
[source,ruby]

‘Enumerable#sum` will set an initial value of `0` (`Integer`) which can lead to a `TypeError`:
as initial value and successively add all following values to it, whereas
When no initial value is provided though, `Enumerable#reduce` will pick the first enumerated value
—-
[’l’, ‘o’].sum(‘Hel’) # => “Hello”
[‘l’, ‘o’].reduce(‘Hel’, :+) # => “Hello”
—-
[source,ruby]

This also holds true for non-numeric types which implement a ‘:+` method:
—-
[].sum(4) # => 4
[].reduce(4, :+) # => 4
[1, 2, 3].sum(4) # => 10
[1, 2, 3].reduce(4, :+) # => 10
—-
[source,ruby]

Autocorrections are unproblematic wherever an initial value is provided explicitly:
@safety
in some Enumerable object can be replaced by `Enumerable#sum` method.
Identifies places where custom code finding the sum of elements

def array_literal?(node) 

def array_literal?(node)
  receiver = node.children.first
  receiver&.literal? && receiver.array_type?
end

def autocorrect(corrector, init, range) 

def autocorrect(corrector, init, range)
  return if init.empty? && safe_autocorrect?
  replacement = build_good_method(init)
  corrector.replace(range, replacement)
end

def autocorrect_sum_map(corrector, sum, map, init) 

def autocorrect_sum_map(corrector, sum, map, init)
  sum_range = method_call_with_args_range(sum)
  map_range = method_call_with_args_range(map)
  block_pass = map.last_argument if map.last_argument&.block_pass_type?
  replacement = build_good_method(init, block_pass)
  corrector.remove(sum_range)
  dot = map.loc.dot&.source || ''
  corrector.replace(map_range, "#{dot}#{replacement}")
end

def build_block_bad_method(method, init, var_acc, var_elem, body) 

def build_block_bad_method(method, init, var_acc, var_elem, body)
  bad_method = method.to_s
  unless init.empty?
    init = init.first
    bad_method += "(#{init.source})"
  end
  bad_method += " { |#{var_acc}, #{var_elem}| #{body.source} }"
  bad_method
end

def build_block_message(send, init, var_acc, var_elem, body) 

def build_block_message(send, init, var_acc, var_elem, body)
  good_method = build_good_method(init)
  bad_method = build_block_bad_method(send.method_name, init, var_acc, var_elem, body)
  format(MSG, good_method: good_method, bad_method: bad_method)
end

def build_good_method(init, block_pass = nil) 

def build_good_method(init, block_pass = nil)
  good_method = 'sum'
  args = []
  unless init.empty?
    init = init.first
    args << init.source unless init.int_type? && init.value.zero?
  end
  args << block_pass.source if block_pass
  good_method += "(#{args.join(', ')})" unless args.empty?
  good_method
end

def build_method_bad_method(init, method, operation) 

def build_method_bad_method(init, method, operation)
  bad_method = "#{method}("
  unless init.empty?
    init = init.first
    bad_method += "#{init.source}, "
  end
  bad_method += if operation.block_pass_type?
                  '&:+)'
                else
                  ':+)'
                end
  bad_method
end

def build_method_message(node, method, init, operation) 

def build_method_message(node, method, init, operation)
  good_method = build_good_method(init)
  bad_method = build_method_bad_method(init, method, operation)
  msg = if init.empty? && !array_literal?(node)
          MSG_IF_NO_INIT_VALUE
        else
          MSG
        end
  format(msg, good_method: good_method, bad_method: bad_method)
end

def build_sum_map_message(send_node, init) 

def build_sum_map_message(send_node, init)
  sum_method = build_good_method(init)
  good_method = "#{sum_method} { ... }"
  dot = send_node.loc.dot&.source || '.'
  bad_method = "#{send_node.method_name} { ... }#{dot}#{sum_method}"
  format(MSG, good_method: good_method, bad_method: bad_method)
end

def empty_array_literal?(node) 

def empty_array_literal?(node)
  receiver = node.children.first
  array_literal?(node) && receiver && receiver.children.empty?
end

def handle_sum_candidate(node) 

def handle_sum_candidate(node)
  sum_candidate?(node) do |method, init, operation|
    next if cop_config['OnlySumOrWithInitialValue'] && init.empty?
    range = sum_method_range(node)
    message = build_method_message(node, method, init, operation)
    add_offense(range, message: message) do |corrector|
      autocorrect(corrector, init, range)
    end
  end
end

def handle_sum_map_candidate(node) 

def handle_sum_map_candidate(node)
  sum_map_candidate?(node) do |map, init|
    next if node.block_literal? || node.block_argument?
    message = build_sum_map_message(map, init)
    add_offense(sum_map_range(map, node), message: message) do |corrector|
      autocorrect_sum_map(corrector, node, map, init)
    end
  end
end

def method_call_with_args_range(node) 

def method_call_with_args_range(node)
  if (receiver = node.receiver)
    receiver.source_range.end.join(node.source_range.end)
  else
    node.source_range
  end
end

def on_block(node) 

def on_block(node)
  sum_with_block_candidate?(node) do |send, init, var_acc, var_elem, body|
    if acc_plus_elem?(body, var_acc, var_elem) || elem_plus_acc?(body, var_elem, var_acc)
      range = sum_block_range(send, node)
      message = build_block_message(send, init, var_acc, var_elem, body)
      add_offense(range, message: message) do |corrector|
        autocorrect(corrector, init, range)
      end
    end
  end
end

def on_send(node) 

def on_send(node)
  return if empty_array_literal?(node)
  handle_sum_candidate(node)
  handle_sum_map_candidate(node)
end

def sum_block_range(send, node) 

def sum_block_range(send, node)
  range_between(send.loc.selector.begin_pos, node.loc.end.end_pos)
end

def sum_map_range(map, sum) 

def sum_map_range(map, sum)
  range_between(map.loc.selector.begin_pos, sum.source_range.end.end_pos)
end

def sum_method_range(node) 

def sum_method_range(node)
  range_between(node.loc.selector.begin_pos, node.source_range.end_pos)
end